Nozzle for liquid injection device and method of producing the same

ABSTRACT

A nozzle for a liquid injection device, wherein a ceramic green sheet ( 11 ) used as a bottom part of a liquid injection device having a nozzle ( 12 ) disposed between a die ( 2 ) and a stripper ( 3 ) storing a punch ( 4 ) and the punch ( 4 ) is moved to form a hole part constituting the nozzle ( 12 ), the green sheet ( 11 ) is disposed between a die ( 2 ′) having a cavity wherein the outer shape of a projected part ( 12   a ) of the nozzle ( 12 ) is reversed and a stripper ( 3 ′) storing a punch ( 5 ) so that it is positioned in the direction opposite to that in the previous disposition and the punch ( 5 ) is moved to obtain the outer shape of the nozzle ( 12 ), and the green sheet ( 11 ) is baked, whereby, even in a drying device to which air is constantly applied vertically to the delivery direction of liquid, no injected liquid is deposited substantially at the tip part of the nozzle ( 12 ).

TECHNICAL FIELD

[0001] The present invention relates to a nozzle for a liquid injectiondevice, a method for producing the nozzle, and a liquid injection devicehaving the nozzle.

BACKGROUND ART

[0002] There has been hitherto known a liquid injection device as adevice for discharging liquid as fine particles. For example, such adevice is disclosed in Japanese Patent Laid-Open No. 6-40030. However,in some cases, air is compulsorily sent to a portion around a liquidinjection hole, i.e., a tip of a nozzle for the purpose of evaporationor drying of injected liquid, concentration of solid componentscontained in the liquid, promotion of momentary movement of the injectedliquid, or the like. Since a tip part of the nozzle is formed to havethe same height as an outer frame of a unitarily molded device as shownin FIG. 3 in each of these devices, liquid injected along the outerframe is prone to form a thin film due to its own surface tension.

[0003] Once such a film is formed, the film acts mutually with liquidsubsequently injected. Therefore, injected particles becomes large orsmall due to evaporation of the injected liquid in the periphery of thenozzle, scattering of injected particles, or an integrated action ofthese phenomena, and thereby injection of liquid as uniform particles ishindered. Under certain circumstances, injected liquid forming a film isdried and sticks to the periphery of a hole of the nozzle. In such acase, since a nozzle has a very small caliber by nature, dried injectedliquid adheres to a tip part of the nozzle, and thereby smooth injectionoperation of liquid is hindered. In the worst case, the nozzle iscompletely clogged, and thereby there is caused a problem of incapabledesired operation, for example, incapable production of a powder havingan aimed particle size in the case of producing a dried powder.

[0004] Therefore, the present invention aims to provide a ceramic nozzlefor a liquid injection device which is free from the problems thatinjection of liquid as uniform particles is hindered because ofevaporation of the injected liquid in the periphery of the nozzle,scattering of injected particles, or the like, due to adhesion of liquidin the periphery of a tip part of the nozzle; injected liquid is driedand adheres to a tip part of the nozzle, and thereby smooth injectionoperation of liquid is hindered; or that the nozzle is completelyclogged, and thereby desired operation is hindered; etc.

DISCLOSURE OF INVENTION

[0005] The present invention has been made in view of the aforementionedproblems and has been completed by finding out that the above object canbe achieved by forming a projected part in a tip part of a nozzle for aliquid injection device.

[0006] That is, as the first aspect of the present invention, there isprovided a nozzle for a liquid injection device, wherein a tip part ofthe nozzle provides a projected part.

[0007] As the second aspect of the present invention, there is furtherprovided a nozzle for a liquid injection device according to claim 1,wherein an internal surface of the projected part is tapered toward aninjection port to be narrower, and a cross-section perpendicular to aliquid injection direction of the projected part is almost circular.

[0008] As the third aspect of the present invention, there isfurthermore provided a method for producing a nozzle having a projectedpart in a tip part, comprising:

[0009] disposing a ceramic green sheet (11) to be used as a bottom partof a liquid injection device to which a nozzle is attached between a die(2) and a stripper (3) storing a punch (4) therein,

[0010] moving the punch (4) to form a hole forming the nozzle in thegreen sheet (11),

[0011] disposing the green sheet between a die (2′) having a cavityhaving a reversed configuration of a projected part and a stripper (3′)storing a punch (5) therein so that the punch (5) is inserted in thegreen sheet in the direction opposite to the direction in which thepunch (4) is inserted in the green sheet,

[0012] moving the punch (5) to obtain a configuration of the nozzle, and

[0013] baking the green sheet.

[0014] As the fourth aspect of the present invention, there isfurthermore provided a method for producing a nozzle having a projectedpart in a tip part thereof, wherein the stripper (3) or the stripper(3′) mechanically stops just before the green sheet (11), and then onlythe punch (4) or the punch (5) is moved to machine the green sheet.

[0015] As the fifth aspect of the present invention, there isfurthermore provided a method for producing a nozzle, wherein said greensheet is prepared by using a ceramic powder having an average particlediameter of 0.2 μm-1.0 μm.

[0016] There is furthermore provided a liquid injection device having anozzle of the first or second aspect of the invention.

BRIEF DESCRIPTION OF DRAWINGS

[0017]FIG. 1 is a partial sectional view for showing a structure of anozzle having a projected part of the present invention.

[0018] FIGS. 2(a), (b) schematically show processes of producing a greensheet for a nozzle having a projected part of the present invention.FIG. 2(a) shows a process of disposing a green sheet 11 between a die 2and a stripper 3 storing a punch 4 therein, FIG. 2(b) shows a process offorming a hole constituting the nozzle in the green sheet 11, FIG. 2(c)shows a process for forming a projected part on the nozzle, and FIG.2(d) is a partially enlarged view of the green sheet 11 in which anozzle of the present invention after finishing the above processes.

[0019]FIG. 3 is a partially enlarged view showing a structure of a tippart of a conventional nozzle.

[0020]FIG. 4 is a schematic view showing a structure of a liquidinjection device having a nozzle having a projected part of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] The present invention is hereinbelow described on the basis ofthe present invention.

[0022] As shown in FIG. 1, a tip part of a nozzle 12 for a liquidinjection device of the present invention forms projected parts 12 a, 12b, and an internal surface the projected part is tapered toward aninjection port to be narrower.

[0023] A nozzle of the present invention has an inner diameter d₁ of 25μm-300 μm, a thickness ti of a green sheet of 50 μm-200 μm, and anaspect ratio of the thickness to the inner diameter (t₁/d₁: hereinbelowreferred to simply as aspect ratio) of 0.5-2.5.

[0024] A method for producing a nozzle of the present invention includesthe steps of: disposing a ceramic green sheet 11 to be used as a bottompart of a liquid injection device to which a nozzle is attached betweena die 2 and a stripper 3 storing a punch 4 therein as shown in FIG.2(a), moving the punch 4 to form a hole forming a nozzle in the greensheet 11 as shown in FIG. 2(b), disposing the green sheet between a die2′ having a cavity having a reversed configuration of a projected partand a stripper 3′ storing a punch 5 therein so that the punch 5 isinserted in the green sheet 11 in the direction opposite to thedirection in which the punch 4 is inserted in the green sheet as shownin FIG. 2(c), moving the punch 5 to obtain a configuration of thenozzle, and baking the green sheet.

[0025] In FIG. 2(c), when the punch 5 is moved down to the lowest point,a clearance between a side portion of the punch 5 and the point p of thedie 2′ is within the range from 2 to 5 times the maximum particlediameter of a ceramic powder forming the green sheet, that is, withinthe thickness range in which the green sheet shows an extreme decreasein strength. If vacuum absorption upon punching the green sheet canprevent refuse from adhering to the hole of the green sheet or fromrising up to the upper surface of the green sheet. It is also effectivein preventing the refuse from adhering to a tip part of the punch. Atapered shape of the die to be wider toward the direction of punching ismore effective. A nozzle can be produced more precisely if the stripper3 or the stripper 3′ mechanically stops just before the green sheet 11,and then only the punch 4 or the punch 5 is moved to machine the greensheet in the method.

[0026] As shown in FIG. 1, a nozzle produced in the above method, acommunicating portion 12 d of the nozzle hole is tapered to be narrowertoward the projected parts. The projected parts 12 a, 12 b are edgeseach having a radius of curvature of 10 μm or less. The tapering isabout {fraction (1/30)}-{fraction (1/10)}. Further, an evading portion12 f locating outside the projected part having r of the nozzle hole,from the projected part 12 b to an evading curved portion 12 e via anupper-end liquid guide portion 12 c having r of the nozzle hole,preferably have a suitable radius of curvature R so as to preventceramics from cracking due to stress upon being baked. Such R is withinthe range from t₁/3 to t₁/10. A tip part of the projected partpreferably has a length corresponding to a radius of curvature R of 12 Carranged to reduce a resistance in flow path. Though a cross section ofthe nozzle portion may be any of circular, oval, square, andrectangular, it is preferably circular in view of workability and liquidinjection efficiency.

[0027] An injection device is generally unitarily baked to produce anozzle having a projected part of the present invention by the use of athus produced green sheet 11. An injection device to be unitarily bakedis produced according to a method, for example, the one disclosed inparagraphs 0010-0013 of the specification for the Japanese PatentApplication 9-335210.

[0028] Since a ceramic material to be used for producing a green sheetemploys a machining method by which a relatively high shearing force isapplied when a nozzle having the aforementioned shape and size, a greensheet having a shearing stress of 2-10 kgf/mm² can be suitably used.

[0029] As a suitable raw material for preparing a green sheet havingsuch a shearing stress, there can be suitably used a material, forexample, zirconia, alumina, silicon nitride, and silicon carbide.

[0030] A method for producing a liquid injection device having a nozzlehaving a projected part of the present invention, where a green sheetproduced in the aforementioned method, is hereinbelow described withreference to FIG. 4.

[0031] A pump portion 21 is formed by stacking a nozzle plate 13 whichis a nozzle portion 11 formed of a thin plate-like green sheet preparedwith a ceramic having an average diameter of about 0.2 μm-1.0 μm andwhich is provided with a nozzle hole 12 formed in the aforementionedmanner; a spacer plate 25 which is formed of a ceramic green sheet andprovided with a window portion 28, and a sealing plate 23 which coversthe window portion 28 by being superposed on one side of the spensorplate 25 and is provided with a liquid inflow port 16. Thus obtainedstructure is unitarily baked.

[0032] On the outer surface of sealing plate 23 of thus obtainedstructure, a piezoelectric/electrostrictive element 22 having a lowerelement 31, a piezoelectric/electrostrictive layer 32, and an upperelement 33 is disposed.

[0033] According to such a liquid injection device, apiezoelectric/electrostrictive layer 32 is deformed, and the cavity(liquid pressure chamber) 15 formed with the window portion 28 beingcovered decreases in capacity when an electric field is generatedbetween the upper electrode 33 and the lower electrode 31, and therebyliquid filling a cavity 15 is injected from the nozzle hole 12communicating.

[0034] As described above, in the present invention, a liquid injecteddevice may be made of zirconia ceramics as a raw material. In this case,a device after being baked is excellent in chemical resistance, thermalresistance, and tenacity. Therefore, even if a solvent for liquid to bedried uses a liquid used for preparing a precursor of a ceramicmaterial, such as acetone type, hydrochloric acid type, or the like, oreven if liquid for combustion is kerosine or gasolin, it is possible touse it.

[0035] Next, specific effects of the present invention are hereinbelowdescribed with an embodiment where a powder is produced by the use of aliquid injection device having such a structure having a nozzle of thepresent invention as described above.

EXAMPLE

[0036] There was used a powder-producing device having a structure shownin FIG. 3 attached to the application of Japanese Patent Application9-335210, on which a liquid injection device is mounted thereon shown inFIG. 4 of the present invention.

[0037] Ethyl alcohol solution of zirconium chloride is intermittentlysprayed inside a quartz furnace 43 having an external heater 42 by anelectromagnetic shutter 41 to give liquid drops. The liquid drops in thefurnace 43 were dried and thermally decomposed to obtain a zirconiaceramic powder A.

[0038] The obtained zirconia ceramic powder A had an average particlediameter of 20 μm and was so uniform that the particle-size distributionwas within +10% of the average particle diameter.

[0039] After the powder was produced, conditions of adhesion of solidcomponents in a tip part of the nozzle were observed, and no substantialadhesion of solid components was found.

[0040] Industrial Applicability

[0041] As described above, in a nozzle of the present invention, liquidinjected at a tip part of the nozzle does not substantially adhere as asolid substance even if the nozzle is mounted in a device to which airis constantly applied in a direction perpendicular to the directionwhere liquid is injected, for example a drying device.

[0042] That is, by using a nozzle of the present invention, there isexhibited an excellent effect of avoiding a hindrance that smoothoperation for discharging liquid is hindered due to sticking of driedinjection liquid to a tip part of the nozzle or that desired operationis made impossible due to complete clogging of the nozzle, or the like.

[0043] Further, in a liquid injection device having a nozzle with aprojected part of the present invention exhibits an excellent effect ofbeing capable of long continuous driving because it does not need tostop driving so as to remove deposites while the device is used sincethe device is substantially free from adhesion of injected liquid whichis solidified in a tip part of a nozzle.

1. A nozzle for a liquid injection device, wherein a tip part of thenozzle provides a projected part.
 2. A nozzle for a liquid injectiondevice according to claim 1 , wherein an internal surface of saidprojected part is tapered toward an injection port to be narrower, and across-section perpendicular to a liquid injection direction of theprojected part is almost circular.
 3. A method for producing a nozzlehaving a projected part in a tip part, comprising the steps of:disposing a ceramic green sheet (11) to be used as a bottom part of aliquid injection device to which a nozzle is attached between a die (2)and a stripper (3) storing a punch (4) therein, moving the punch (4) toform a hole forming the nozzle in the green sheet (11), disposing thegreen sheet between a die (2′) having a cavity having a reversedconfiguration of a projected part and a stripper (3′) storing a punch(5) therein so that the punch (5) is inserted in the green sheet in thedirection opposite to the direction in which the punch (4) is insertedin the green sheet, moving the punch (5) to obtain a configuration ofthe nozzle, and baking the green sheet.
 4. A method for producing anozzle according to claim 3 , wherein the stripper (3) or the stripper(3′) mechanically stops just before the green sheet (11), and then onlythe punch (4) or the punch (5) is moved to machine the green sheet.
 5. Amethod for producing a nozzle according to claim 3 or 4 , wherein saidgreen sheet is prepared by using a ceramic powder having an averageparticle diameter of 0.2 μm-1.0 μm.
 6. A liquid injection device havinga nozzle having a projected part according to claim 1 or 2 .